1. Field of the Invention
The present invention relates to semiconductor devices and, more particularly, to a memory card used as data storage media.
2. Description of the Related Art
A multimedia card (MMC) is one of new memory cards for use with portable electronic devices. Such a memory card employs a control device and a memory device, both of which are mounted on and electrically connected to a printed circuit board or a card substrate, using a wire bonding process. The MMC is protected from an external environment using encapsulating structures formed by a molding process, a capping process, or both.
FIG. 1 is a plan view of a conventional memory card. FIGS. 2a to 2c are cross-sectional views of the conventional memory cards.
In the conventional memory card 110, a memory device 111 and a control device 115 are mounted on a card substrate 120 and encapsulated as shown in FIG. 1. The conventional memory cards can be classified into three different types depending on their inner structures as discussed below.
FIG. 2a shows a conventional memory card 210, in which a packaged memory device 211, a packaged control device 215 and a passive device 217 are mounted on a card substrate 221 and then encapsulated with a lid 243.
FIG. 2b shows another conventional memory card 310, in which a bare (non-packaged) memory device 311 is mounted on and electrically connected to a card substrate 321 through a bonding wire 325 and encapsulated with a molded body 341. Like the memory card 210 of FIG. 2a, a packaged control device 315 and a passive device 317 are mounted on the card substrate 321. Finally, the devices 311, 315 and 317 are all encapsulated with a lid 343.
FIG. 2c shows yet another conventional memory card 410, in which a non-packaged memory device 411 and a non-packaged control device 415 are mounted on and electrically connected to a card substrate 421 through bonding wires 425a and 425b, respectively. All of the devices 411, 415 and 417 are protected by both a molded body and a lid.
As mentioned above, the memory device and the control device are any of packaged or non-packaged and mounted on the card substrate in a two-dimensional arrangement. If the memory device and the control device are assembled into packages, a surface mounting technology (SMT) is used to interconnect the devices with the card substrate. If the devices are bare chips, i.e., not assembled into packages, a wire bonding technology is used to interconnect the devices with the card substrate. Either way, each device is finally capped with the lid to be protected from an external environment to improve the reliability.
Such conventional memory cards are manufactured by mounting the memory device and the control device on the card substrate and then capping the devices with the lid. While the packaged devices can be simply surface-mounted, the bare chips need to be wire-bonded and encapsulated with a molding compound between the mounting and the capping steps.
The conventional memory card is, however, limited in its ability to increase memory capacity and to reduce size due to its two-dimensional arrangement. Also, because the devices within the conventional memory card are protected by both the lid 443 and the molded body 417, manufacturing process steps are complicated and manufacturing costs are increased.